I don't think it's bad if You play those covers different - less or more. The main thing is that the band sounds ok. Otherwise there is no much point covering songs exactly the same way they sound original. And what You say that You play from what You feel - wonderfull. The only thing is that Your band plays the covers in absolutely different genres, like (original - funk, Your band - metal), then You must calm down a little and think more of your notes.
For me the reaggea is fine. Very relaxing music. The only thing is that i can't listen to it more than 2,5 hours. It starts to sound too the same to me, but as i said, reggea is cool.
Anything could be possible, but the easiest way to find fast your nearest shops who do out music instrument renting, that would would be the best and cheapest solution. Chech the brands and models available, think of the days and do it, used or new you would find a good choice for the money you have.
Each has his own best setup, so just calm down and try to feel the dead spots and then configure Your best setup in Your head at first, then think twice and do it.
In my country Latvia - to get further at Eurovisio it is no chance for rock, metal, jazz, latin. Only perfectly balanced pop, soul or disco with superbably writen words that slime together in each part. No other way, believe me i have tried a lot.